| At a glance | Placenta covering or near the internal cervical os — painless bright red bleeding in second/third trimester. | Premature separation of the normally implanted placenta — painful bleeding with uterine hypertonus and fetal distress. |
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| Classic presentation | Third-trimester woman with painless bright red vaginal bleeding, soft non-tender uterus, and placenta over or near the cervical os on TVUS.; Painless bright red vaginal bleeding in the second or third trimester (classic — sentinel bleed); Often unprovoked; can follow intercourse; Bleeding may resolve spontaneously, recur, or be massive;… | Third-trimester woman with painful dark vaginal bleeding, firm tender uterus, and nonreassuring fetal heart tones — especially in setting of hypertension or trauma.; Sudden onset abdominal/back pain; Vaginal bleeding (dark red; absent in ~20% — concealed abruption); Uterine contractions or hypertonus; Decreased fetal movement; Symptoms… |
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| Workup / key labs | AVOID digital cervical exam in any patient with third-trimester bleeding until placenta previa is excluded by ultrasound.; CBC, blood type and crossmatch, coagulation studies; Kleihauer-Betke if fetomaternal hemorrhage suspected and mother is Rh-negative | CBC, blood type and crossmatch; Coagulation studies (PT, PTT, fibrinogen — pregnancy normal >300-400 mg/dL; <200 concerning, <150 critical); DIC panel: fibrinogen, D-dimer, FDP, platelets; BMP, LFTs; Kleihauer-Betke for fetomaternal hemorrhage and dosing of anti-D; Urinalysis (toxicology if substance use suspected) |
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| Imaging | Transabdominal ultrasound first, then transvaginal ultrasound — safe in placenta previa and more accurate; gold standard for diagnosis; Routine anatomy scan at 18-22 weeks identifies most cases; many low-lying placentas resolve by third trimester; Repeat ultrasound at 32 weeks for previa identified earlier; MRI if placenta accreta… | Continuous external fetal monitoring — most important assessment; Tocodynamometry — high-frequency low-amplitude contractions or hypertonus; Ultrasound — retroplacental hematoma visible in only ~25-50% of cases; absence does NOT rule out abruption; Placental abruption is primarily a CLINICAL diagnosis |
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| First-line treatment | Avoid digital cervical exam, intercourse, vaginal tampons; Activity restriction (modified — strict bedrest no longer recommended); Hemodynamic stabilization with IV access, type and screen, transfusion as needed; Inpatient management for active bleeding; outpatient with strict precautions and proximity to hospital for asymptomatic… | ABCs — large-bore IV access, type and crossmatch (4-6 units), IV crystalloid resuscitation; Continuous fetal monitoring; Left lateral decubitus positioning, oxygen; Foley catheter — strict input/output; Lab studies including coagulation; Anti-D immunoglobulin for Rh-negative women |
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